Abstract : A Scanning lidar has been modified to operate aboard the research vessel GLORITA in the MAST (Monterey Area Ship Track) experiment. Beam pointing stabilization was accomplished by using vertical gyros to measure the ships' attitude and a computer to control the scanning mechanism. The computer reads angles from the scanning mechanism, gyros and data acquisition computer which determines the desired pointing direction. Using orthogonal transformations, the required position of the scanning mechanism is calculated and appropriate commands are sent to it. During most of the MAST experiment the wave heights were in the 3 to 7 m range with rolls reaching 200 and pitches reaching 70 For these conditions, pointing accuracies of 0.10 were achieved. (MM)